Re: Snow on telly - Results :-(
> RESULT: The TV interference was much brighter on my TV and one
> several houses away. This made me think that noise
> generated in the spark-gap and primary circuit is the
> cause of the problem.
>2. Tried listening on an AM radio (not tuned in to anything,) and had
> a mate walk down the road with the radio to investigate the extent
> of the radiated interference. My friend walked about 150 yards
> away from the coil.
> RESULT: He said that he could hear the raspy crackling sound
> of the TC anywhere on the AM band at 150 yards away.
> He turned around and walked back because it had not
> begun to fade away !
> ( Since I am an electrical engineer by profession I
> was greatly disturbed by this and decided to limit
> individual run times to around 1 second until the
> problem could be rectified.)
>5. Tried an RC snubber across the RQ spark gap and then across the
> primary winding. Snubber consisted of a rolled poly 600pF cap and
> a bunch of parallel Carbon Film resistors (R = 150R.) This should
> reduce the Q of spurious UHF resonances in the primary arrangement
> by absorbing the high frequency energy.
> RESULT: No noticeable difference. The Resistors did get warm
> though, so some power was being absorbed when it was
> connected across the spark gap.
I belive carbon film resistors are spiral cut and therefore inductive.
>7. Tried shielding the spark gap and fans in an grounded Al foil
> covered box.
> RESULT: No noticeable change to interference.
If you have access to a good(and I mean GOOD) spectrum analyser I recomend
you try to figure out where the noise energy is concentrated. I have a
sneaking suspicion that the noise your dealing with isn't realy in the AM
band or the TV bands at all. I suspect that the pipes in your RQ gap plus
the nonlinear resistance of the spark are forming a high powered microwave
oscillator.(a parametric amp if you will.) The funny thing about microwave
noise like this is that it is almost "unstopable". It can squeaze through
all but the smallest holes. It will radiate directly into any consumer
appliance and use the trace wires for antennas. Anything that rectifies(like
the detector diode in any reciever) will be pumping charge one way. It can
couple through the parasitic capacitance of a normal line filter. The
parasitic L of any cap with wire leads looks like an open circuit. Things
get strange fast after 1GHz. If your using 3/4" copper pipe it could be
oscillating from side to side which would give a frequency of 7-8GHz. It
could also be oscillating at a harmonic like 14-16GHz or higher order
harmonics. Or some frequency related to the length of your pipes.
Hope this doesn't scare anyone too much.